Lever actuated and anchored brake



Dec. 22, 1964 R. T. BURNETT 3,162,273

LEVER ACTUATED AND ANCHORED BRAKE Filed May 6. 1960 9 Sheets-Sheet 1 IN VENTOR.

RICHARD 77B URNE T7 ATTORNEY Dec. 22, 1964 R. T. BURNETT LEVER ACTUATED AND ANCHORED BRAKE 9 Sheets-Sheet 2 Filed May 6, 1960 INVENTOR. RICHARD T BURNETT 2,2, 4. M ATTORNEY Dec. 22, 1964 R. T. BURNETT 3,162,273

LEVER ACTUATED AND ANCHORED BRAKE Filed May 6, 1960 9 Sheets-Sheet 3 INVENTOR. RICHARD 7T BURNETT ATTORNEY Dec. 22, 1964 R. T. BURNETT 3,

I LEVER ACTUATED AND ANCHORED BRAKE Filed May 6, 1960 9 Sheets-Sheet 4 INVENTOR.

R/CHARD T: BURNETT ATTORNEY Dec. 22, 1964 R. T. BURNETT 3,162,273

LEVER ACTUATED AND ANCHORED BRAKE Filed May 6. 1960 9 Sheets-Sheet 5 INVENTOR.

ATTOR Dec. 22, 1964 R. T. BURNETT LEVER ACTUATED AND ANCHORED BRAKE 9 Sheets-Sheet 6 Filed May 6. 1960 INVENTOR. [CHAD w: URNETT AT TORNE Y Dec. 22, 1964 R. T. BURNETT 3,162,273

LEVER ACTUATED AND ANCHORED BRAKE Filed May 6, 1960 9 Sheets-Sheet '7 INVENTOR.

RICHARD T BURNETT BYWdW AT TORNE Y Dec. 22, 1964 R. T. BURNETT LEVER ACTUATED AND ANCHORED BRAKE 9 Sheets-Sheet 8 Filed May 6, 1960 INVENTOR. RICHARD T B URNET T 20%- J. W ATTORNEY Dec. 22, 1964 R T. BURNETT 3,162,273

LEVER ACTUATED AND ANCHORED BRAKE Filed May 6. 1960 9 Sheets-Sheet 9 I; (in.

40/ 64 261/ m (C 4a;

l 0 O O 0 I 500/ Q i 252 QOd I' O 250 m I INVENTOR.

RICHARD T BURNETT AT TORNE Y United States Patent ()fiice 3,162,273 Patented Dec. 22, 1964 3,152,273 LEVER AQTUATED AND ANCHORED BRAKE Richard T. Burnett, South Bend, ind, assignor to The Bendix Corporation, a corporation of Delaware Filed May 6, 1964 Ser. No. 27,327 21 Claims. ((31. 188-78) This invention relates to brakes which are especially adapted for high torque capacities such as those normally required by heavy duty trucks, busses, trailers, and the like.

A substantial number of heavy duty truck brakes now in use comprise fixed anchor non-servo shoe type brakes actuated by a pneumatically operated S-cam which effects spreading movement of the shoes. The required capacity of the brake is obtained by simply enlarging the brake parts to the point where they can provide the heavy braking forces necessary to control vehicle movement. As a result, the brake tends to be extremely bulky and heavy weight. What the brake lacks in inherent effectiveness is compensated for by enlargement of the parts so that they will be adequate. As a result, since the brakes are part of the unsprung load of the vehicle, larger axles are required because of the bulk and weight of the brake. The described brakes are costly because of their large size and this leads to over-all vehicle cost. Although this situation has existed for many years, no one, prior to the present invention, has proposed an acceptable light weight construction brake, which will meet the high torque requirements of heavy duty vehicles.

Accordingly, it is a primary object of the present invention to provide a small light weight brake which is more economical to produce than the presently used fixed anchor non-servo shoe type brakes and which will yet have the necessary torque capacity by means of components which are arranged and constructed mor efficiently to meet the brake requirements of the vehicle.

It is a further object of the invention to provide a heavy duty, light weight brake with an adjusting means for the brake shoe which will compensate for wear of the shoe but independently of the actuating means. Since the brake shoe adjuster and the shoe operating means are independent, the stroke of the actuating means is not increased by expansion of the shoes from adjuster operation as is the usual case.

Another object of the invention is to provide a light weight effective brake having floating brake shoes with the center of engagement pressure between the shoes and the opposing drum surface located substantially midway between the ends of the shoes to provide a lining wear pattern which utilizes a greater proportion of the shoe lining and hence is more eflicient, the brake being substantially equally effective in both forward and reverse drum movement to obtain a symmetrical brake structure.

It is a further object of the present invention to provide a novel actuating and anchoring means utilizing a system of levers which can be proportioned to obtain the centerof pressure between the shoe and its opposed drum surface, substantially midway between the ends of the shoes. There results a more efiicient utilization of the lining and an equal effectiveness of the shoe for forward and reverse directions of rotation of the drum.

association between a lever, utilized to transmit actuating force to a brake shoe, and the brake shoe for axially positioning said shoe relative to a brake drum.

Another object of the invention is to utilize space within the brake more efiiciently so that a wide variety of different actuating means may be provided, including hydraulic actuating means, pneumatic actuating means, and force transmitting means between the shoes, including linkage for effecting servo action and/or equalized servo action.

The actuators in the present invention are adapted to the fixed motion of the leverage system rather than the irregular free floating movement of the shoes, and this makes possible the equalizing lining wear pattern previously described and also a more efficient utilization of brake space whereby it is possible to select the actuating means, viz., hydraulic, pneumatic, or mechanical which is best adapted to the particular usage.

Other objects and features of the invention will become apparent from a consideration of the following description, which proceeds with reference to the accompanying drawings, wherein:

FIGURE 1 is a side elevation view of a two leading shoe brake which is hydraulically actuated by a pair of double acting wheel cylinders;

FIGURES 2, 3, respective section lines 2--2, 33, and 44 of FIG- URE 1;

FIGURE 4A is a force diagram of the brake shown in FIGURE 1, illustrating the anchoring area applying forces on the shoe and the resultant drum reaction force.

FIGURE 5 is a side elevation view of a pneumatically actuated brake having one pair of the adjacent shoe ends connected by a linkage which transmits applying force between the shoes in substantially the same amount provided by the pneumatic actuator;

FIGURES 6 and 7 are section views taken on the respective sections 66 and 77 of FIGURE 5;

FIGURE 8 is a side elevation of the brake having two pneumatic actuators, one for each of the opposite pairs of ends of the shoes;

FIGURES 9, 10, and 11 are section views taken on respective section lines 9- 9, 10-10, and 1111 of FIGURE 8;

FIGURE 12 is a side elevation view of a brake in accordance with the present invention which is of a nonservo configuration, i.e., one shoe is a leading shoe while the other shoe is a trailing shoe in each direction of drum rotation; and,

FIGURE 13 is a further embodiment of the invention showing in side elevation view a servo brake incorporating principles of the present invention, in which the tangential Wiping action of one of the shoes is transmitted to the other shoe as applying effort thereon, this brake being the most effective of the various brake configurations for an equivalent weight of the components.

Referring now to the embodiment shown in FIGURES 1 to 4, the brake, designated generally by reference numeral 10, includes a rotatable brake drum 12 having a cylindrical braking surface 14 and a pair of identically constructed brake shoes 16 and 18 each including an arcuate rim 20 having friction material segments 22 and 24, and two transverse strengthening webs 26'and 28.

The shoes are carried by a torque plate 30 which is fastened by a ring of bolts 32 to a nonrotatable part of the vehicle, as for example, an axle flange (not shown). At each shoe end is a lever 36 which is mounted for pivotal movement on anchor pin 38 received through torque plate 30. The anchor pin 38 is riveted at end 40 (FIG. 2); a retaining ring 42 and washer 44 retain the lever on the enlarged diameter section 45 of anchor pin 58. At the end of each lever opposite its pivotal mountand 4 are section views taken on the,

yvith the applying force F locates the drum n U; V V ingis an abutment 45 formed from a turned up portion of the torque plate, and is located to engage end 48 of p the lever whereby the lever. is supported at each of its opposite ends as it receives the anchoring load of the associated brake shoe. H i Ii Referring to FIGURE 4A, the anchoring force F 'is shown at the upper end of the brake shoe, the condition which exists during braking with-counterclockwise drum. 7

rotation, Y The anchorin'gforce acts perpendicularly to the surfaces of engagement between lever 36- and its shoe end. By controlling the configuration, of the, anchoring surface 50 of the lever, i.e., by suitably disposing the angu together re action the direction of the anchoring force F which,

force R, which originates at the intersectionof force P and anchoring forceF and is at an 'angle such that an extension of P is tangent to the friction. circle whose center is the geometrical center of the brake.

The radius of the friction circle is derived from the cois obtainedfrom the value v sin (arctan [1.) Where I a is the coefiicient of friction and 7 'y=distance'from the center of the brake to the point P '7 which is defined as the location'ot' intersection of radius 'y with P such that theiangle x=arct-an and n is ;the V coefiicient of friction previously described.

The point of intersection of P with the shoe surface is considered the center of pressure and .to' the extent that the center of pressure may be brought midway between i the endsof the shoes then greater'utiliiation of the lining segments i's provided- The appropriate disposition of P is then obtained by means oftappropriate configuration of pp y ng larity of the anchoring surfaces, it is possible to locate .efiicient of {friction of the lining segments 22 and 24 m lanchoring'force passes through the shoe at some preferred location, See. for example, US. Patent No. 2,822,065

issued February 4, 195 8 ;'U.S. Patent No. 2,269,268 issued January 6, 1942;; and US. Patent No. 2,755,889 issued July 24, 1956 for various examples of the described anchoring arrangement.

1' Each shoe web 26. and 28 hasa portion 54'overlying its actuating 'leverto'lassist in axially positioning the shoe integrally with stem 72 which extends through one of the webs of the shoe and is fastened to a sleeve 73' and is turnedmanuallyto effect adjustment. Thus, the stem'72 is turned; rotating the star wheel 68 which canslide axially along the shank of bolt 58.:and. also cause the bolt 58 to turn. Since the nut 60 is held against the shoe, the nut 60 will travel along the. length of the bolt 58 away from the lever 36, and bring the lining'segments 22 and 24 closer to the cylindrical surface 14. Since both shoe ends are slidable, only. one shoe end, need be manually adjusted because the shoe can slid on its ends to relieve overadjustment. at either end and the lining segments will thereby conform with the opposed cylindrical drum surface 14.

The shoes are held in their normally retracted; position i by meansof four return springs 74' which are stretched betweenadjacent shoe ends, urging the shoes radially inwardl-y'to disengage lining segments 22 and '24 from the surface 50 which determines the sense of F,,. The length F is a measure of theoutput'of the-brake and theratio of E, to F is a measure ofthe effectiveness ofthe brake.

As the drum reaction force'F moves closer to the anchor it increases proportionally to F and hence the cylindrical braking surface .14. The spring force, acting through the shoes; tends to pivot each leverin suchdirection'that' its end 43 engages the fixed abutment 46 so that the retracted position of the shoes .isdefined by pivotal movement of the lever 36 into engagement with fixed brake becomes more effective but less controllable. The

configuration of'su'rfac'e 50 is thus important'in' (a) locat-. irig the center of pressure to 'obtainna'n optimum pattern of. Wear (b) it determines the appropriate, degree of brake effectiveness and c) the appropriate degree of con-a trollability. For conveniencethe braking surface is referred to hereinas a radialsurface but the importance of such construction lies not iiiits being coextensive with Y a radius (intact it is only approximately so) but rather in the proper location of the resultant drum force F relatively to the brake shoe. These surfaces 5i) on the levers provide both pivotalfand sliding'movem'ent of the 7 shoe ends thereon. Generally speaking, in'other brakes,

the center of engagement pressure between the drum surface and'the'shoe friction lining is at the heel'or an least amount at the toe to the, greatest amount :at the j heel results in'ineflicient'utili z'ation of the lining. Because the point of greatest engagement pressure is approximately r'nidway betweenthe shoe, ends the taper of the lining is abutment 46.

; As will be seenfrom a considerationiof all of the embodiments, a variety-of actuating means may be provided betweenthe ends'of the shoes to Ioperate the levers which communicate applying or, actuating force on the shoe ends; the'particular actuating means shown in the embodi- .ment ofPIGURES 1 to 4 compri's'es hydraulically operated wheel cylinders 89 each including two oppositely acting pistons 82 with piston-nods 8j4 connecting the piston and lever 36. Each pistonhasthe usual sealing cup 86 with aspring 88 keeping the cups seated. Inlet ports I 90 and-92 are also included fortheir usual function.

- In brake operation, assuming counterclockwise rotation 1 of the drum corresponding to forward vehicle movement, the brakeis actuated by communicating fluid pressure to, 55 chor'ed end of the shoe. Since the shoe must be serviced when the lining wear reaches the. rim alongany portion of the rim, the pattern of lining We'arEprogressing from the thetwo wheel cylinderswhichlpivot levers36 on bolts 38 causing the friction segments 22 and 24 of-shoes '16 and 18 to engage-the cylindrical surface14 of the drum 12. Shoe I 16 anchors at its left handend (FIGUREJ) on its lever 36.;and shoe 18 anchors at its right'hand end on lever 36.

The two shoes each pro'vide leading shoe; braking, that is to say, both are self-energizingand each'does an equal amount of braking work 'so vthatmaximum utilization is obtained of each brake shoe. Since each shoe is self-enshoe and the greatest lining thickness is providedjmidway along the arcuate length of thefshoe. The-present inven .tionfis the first instance of utilizing lever actuationiwith' i s 1n both forward andreverse drum rotation with the cent'er 1 of pressure located substantially in the optimum position a described. 7 Q j While previous structures have. included radialfxanchoi' 1 ing surfaces to control the brakingpefi'e'ctivene'ss and'sel'ecfloating shoe arrangement, having equaleffectiven'es er'giz'ing, there is provided a maximum degree-of individual braking action. 7 V ce'ives the anchoring load of the shoe is'held at each of its opposite ends by; the" pivot bolt 38 and abutment 46 the a "anchoring load is distributed between two points and the ,structure for taking the braking load may therefore be madecorrespondinglysmaller because'thc. load. is not 1 concentratedat agsingle location. Since theshoe is .free

tivelylocate the point of maximum weanjjthese prior-struc tures are;concerned with fixed anchoring means having'j their-faces so disposed-to the brake shoe that the resultant- 'bothto'pivotandslide at its anchoredehd atthe point of engagement with thelev'er 36*the re is a freeffloating shoe action a which permits the Y "friction; segments to conform with-Qt'heijpposed cylindrical surface 14 0f the -d rum,'thus Because the lever' 36 which-repreventing pinching of the lining and localized Wear of the friction segments. In other words, the wear pattern is more evenly distributed over the entire arcuate length of the friction segments. s

' I am aware that location of this center pressure has been located in previous construction by means of suitable construction of the anchoring surface and the considera tions involved in computing the appropriate location of the anchoring surface is a matter of general knowledge to those skilled in the art and therefore I do not assert this to be a part of the present invention. What is significant in the present invention however is that the anchoring surface may be constructed in a lever which also serves as anactuating means so that the brake can be equally effective in both forward and reverse directions of drum rotation.

Referring to the actuated ends of shoes 16 and 18, viz., the right hand end of shoe 16 and the left hand end of shoe 18, the piston 82 acting through its piston rod 84 functions to turn the lever 36 and turning of the lever is communicated as applying effort on the shoe end. Because the applying force of the wheel cylinder is multiplied through the lever, then the diameter of the piston may be reduced, this being a significant factor because in heavy duty brakes radial space in the brake is generally most critical. As a result, smaller diameter cylinders may be used between the cylindrical drum surface and the mounting bolts. Because movement of the pistons is related to the pivotal movement of the levers which is a fixed type movement, rather than an erratic and irregular shoe movement, this simplifies the construction and design of the wheel cylinder actuator and makes it possible to substitute a variety of different actuating means, as will be seen in later embodiments of the invention. Usage of the lever 36 does necessitate a somewhat greater stroke of the piston but such increase is not prohibitive and additional piston stroke is not required to follow up wear of the lining. Since, in the case of heavy duty brakes, the lining segments may be in the order of in thickness it would be prohibitive to meet piston stroke requirements for both lever movement and lining thickness. Accordingly, a novel arrangement of the adjusting means 56 is provided wherein the adjuster is located between the end of the shoe and the lever 36 so that the shoe may be moved closer to the drum to compensate for wear but without adding to the stroke requirement of the piston for actuating the shoe. Thus, with the levers in their fully retracted position shown in FIGURE 1, the piston stroke requirement is that necessary to take up the lining clearance shown in FIGURE 1; and, if the lining wear were to be substantially down to therim, it can be seen that the adjusters will move the shoe away from the levers to compensate for such wear so that the running clearance is reestablished and the same piston stroke will produce brake engagement unaffected by such adjustment.

' When the brake is released, fluid pressure in the wheel cylinder is relieved and the return springs 74 fastened between the shoe ends draw the shoe ends together thereby pivoting the levers 36 until they are brought into engagement with abutments 46, thus defining the fully retracted position of the shoes. During reverse vehicle movement, with the drum rotating clockwise and the wheel cylinders are energized, the right hand end of shoe 16 is anchored and the left hand end of shoe 18 is anchored. Both shoes are self-energizing and the levers are each identically con-' 'structed and therefore each has the same lever ratio.

The brake is therefore equally effective in reverse and forward braking. Owing to the fact that each brake shoe 'does an equal amount of work and because of the more widespread distribution of the anchoring and actuating I actuated non-servo S-cam brake but in the order of 6 pounds less weight, thus effecting a saving of material and, hence, cost of construction. This 35 pound weight saving per brake also decreases the unsprung Weight of the vehicle and permits smaller axles, etc.

Referring next to the embodiment shown in FIGURES 5 to '7, there is illustrated substantially the same leverage system of actuation as in the previous embodiment but with pneumatically operated means as distinguished from the hydraulically operated means shown in FIGURES 1 to 4. In this embodiment the structure corresponding to that of the previous embodiment will be referred to by the same reference numeral but include further the subscript a. The two brake shoes 16a and 18:: each include an arcuate rim 20a and two transverse strengthening webs 26a and 28a, there being friction material segments 22a and 24a which are eccentrically ground so that maximum thickness of the lining segment is approximately midway between the ends of the shoes at the point of maximum pressure of engagement between the lining segments and the opposing cylindrical surface 14 of drum 10a. At the one pair of adjacent shoe ends is a pneumatically operated actuating means 98 which pivots levers 36a on their fulcrums 33a fastened to torque plate 3% which is fastened by bolts 32a to a nonrotatable part of the brake structure.

Between the other pair of adjacent shoe ends is a connecting linkage 160 which transmits the anchoring load of one shoe as applying effort on the other shoe. The linkage is mounted between two levers 101 against which the shoe ends directly bear to transmit anchoring load or receive applying thrust depending upon the direction of drum rotation. The linkage is designed so that the anchoring load of the one shoe is transmitted as applying etfort to the other shoe to develop equal applying thrusts on each shoe. This arrangement is sometimes referred to by those skilled in the art as controlled servo and the net efiect of the linkage 100 is to serve as a replacement for a separate actuating means to obtain greater construction economy. The particular linkage forms the subject matter of a separate patent application and is illustrated herein only to demonstrate the latitude of invention for the novel leverage system for actuating and anchoring the brake.

The shoes are held in a normally retracted position by means of looped leaf springs 102 which are fastened to the torque plate 36a and bear against the ends of the shoes that are combined with the pneumatic actuator, the ends of the shoes combined with linkage 100 being held thereagainst by means of leaf springs 104 which are fastened to levers 191 at one end and are biassed at the other end against the bolt head of the manual adjusters 56a fastened to the brake shoes. The levers 101 are held together by two springs 103 which bottom the linkage in the levers to return the shoes.

The adjusters 56a are essentially the same construction as provided in the previous embodiment and identified in FIGURES 3 and 4. The particular adjuster construction is not an essential part of the present invention and may consist of any of the well known manual adjusters, the only requirement being that the adjuster must have sufiicient strength to resist the anchoring load of the shoes and be located between the levers and the shoes.

Referring to FIGURE 6, each pneumatic actuator includes a pneumatic chamber and flexible diaphragm 112 which is clamped between the two halves 114 and 116 which form the housing, these two halves being held to gether by a clamping band 118. The diaphragm thrust member 126 is operatively connected to a link 122 having a wedge 124 at the end of the link. The spring 126 maintains the diaphragm thrust member in a normally retracted position and spring 128 acting through a washer 130 biases the link 122 rightwardly (FIG. 6) whereby the wedge 124 is withdrawn from the brake assembly. 1

The pneumatic actuator is mounted on the torque plate through a sleeve 134 which extends through an opening crum 38 and abutment 46a.

in the cover plate 135 which covers the open end of the .drurn 10a. The housing: can be'adjusted for initial positioning by means of a nut 138 which is turned down to i move the wedge 124 farther into the brake assemblyo'r;

out of the brake assembly so that the Wedge will have no clearanceas initially installed. f The two clamping'nuts 149 and 142 prevent accidental: turning of thejnut 138 once it'is in its proper operative position.

The torque plate' 30a is turned back at 156 to provide the abutments 46a which limit turningimoverrientof: the levers 36a and thus distribute the anchoring, load between the fulcrum, 38a and abutment 46a. A member J16) formed integrally with fulcrurns 38a fastened to axle flange 162 by bolts;164 carries a plate 166 which is fastenedto 150 by means of interlocking portions 168, the

links 174 and levers 3&2. Thus, as shown inFIGURE 7 the wedge 124 is thrust in a direction normal to shoe movement, cam followers I'Nlwillrock within sockets of levers 36a and the lateral component of thrust by-the wedge 124-is resisted by rocker links 17 4. i

The levers 36a b'ear'against hardened inserts 176 which are fastened by bolts 178 between the webs 26a and 2&1.

In 'brake operation, whenpneumatic pressure is com municated-to the chamber 110 the link 122 .1is moved toward the brake" cavityso that, Wedge 124 forces thecam followers 17% apart, causinglevers 3&0 topivot on their fulcrums 38a. Assuming counterclockwise rotation of the drum corresponding to forward vehicle movement, the shoe 18a (FIGURE 5) anchors at its right handiend on lever 36a and the anchoring force is communicated through linkage 100 in such amount that the applying effort developed by lever 101 at the right' handend of lining thickness} AocordinglyQfro rn the resulting wear pattern, maximumfutility. is obtained from the lining he'- fore'necessity of replacement? Wheu a brake adjustment is needed,.the adjusters 56a betweenthelinkageltlti and the. shoe' ends are manually-operated to rte-establish the original running clearance b'etween the friction segments -"and the opposing cylindrical surface lddfaof the drum.

. Since thefadjustment is made between the shoe end and the linkage 189,. linkage movement does'not increase beyondthat required-at the tirn'e 'of brake" adjustment, i.e. the linkage is substantially uiiafiected by progressive j Wear of the brake lining, and since the shoes are free floating shoes constructed for pivotal and sliding move purpose of the plate 166 being to laterally position rocker g Lment at each of their oppositeend's, the'brake'adjust ment will not add to: the wedge movement necessary for eifectingfull brake, application. As before described,

it as actuator 'movement is' in accordance'with the prescribed pivotal movement of. the levers 36a and does not follow the erratic and irregularymovementzof the shoe ends and therefore the actuatingineans is simplified in 7 its operationbecause ofitsindependenoe from shoe movement. Such applying action is ideally suited for the reciprocable wedge movement obtained by pneumatic actuators. I

' Referring'neXt to the embodiment shown in FIGURES 8 toll, there islillustrat'ed a further embodiment of the 1 invention employing two pneumatic actuators, one be.--

, .t'ween; each of the opposite adjacent pairs of shoe ends.

In this embodiment, asin the previous embodiment, the two brake shoes areidentical and therefore parts corresponding tothose in the, prior embodiments .will be referredto by the same reference numeral but will in- V elude further the subscript b.

shoe 16a is substantially equal in amount'to th'e apply-j ing etfort developed at the left hand end of shoe 18a.

Shoe lfia'then' anchors at its left'hand end on lever 36a which resists the anchoring load distributed between ful- The two shoes 16a and 18a thus do .an approximately equal amount'o-f braking work and both are equally effective. I i

of the brake shoes'are app-lied at their leading ends and anchors at-their trailing ends, thisbeing accomplished. by

means, of the servo linkage. 100,,interconnecting'two of the adjacent shoe ends. The fact that the anchoring load I is sustained by a lever having two supports which share the anchoring load makes it possible to distribute the anchoring forces overa greater area and thi-s makes the" j brake of a greater torque'capacitywithout mere enlargement of'the brake parts. When the brake is released, the wedgeis returned by mearisiof spring 128, there The two brake shoes 16band: 18b include an arcuate .gnnesband vtwo'transverse strengthening'webs 26b and "23b, theftwo shoes being actuated into engagement with the a cylindrical surface 1411;. of the rotatable drum 1% V by meansof levers 36b whichare mounted for pivotal 5 Although only one actuating means is provided both movement on anchor pins 3812 received within torque plate 305. At the end of the lever opposite its pivotal mounting is 'an abutment 4'6b just in, the previous embodiments and the anchoring load of theshoe when it anchors against the lever isdistributed between the abutment 46b andtheanchoripin 38b so that the anchoring stresses are not localized atany one point. I Also,

- V similarly tolhe" previousembodiments, a. manually operated adjuster 56b is disposed between one shoe end and being insome instances four supplementary'springs 13d which are loaded by movement of the wedge 124 in a direction to apply the brake. When the brake is released 1 leaf springs 102 return the ends of: the shoes "combined with the pneumatic actuator 98: and springs'ltlla'retract retracted position. i

When the brake is ment correspondingto, clockwise, drum rotation, the end the other pair of adjacent shoe ends and'leyers to a fully applied with reverse vehicle move? 60 its 'leyer 36b... sorth'a't 8.31116, lining wears, the original running clearance ,between the friction segment and opposinldrun'i' surface can be reestablished by operation of th "adjusting means; The ends of the shoes are in pivotal and I-in'jsliding engagement with inclined surfaces 7 of the levers'which provide anchoring surfaces for the of shoe 16a combined with thepneumatiqactuator 98;,

is the leading end andthe end of shoe 143 1.operatively shoeend, these inclined surfaces being proportioned and located so. that the center of pressure between the lining and thedrurn is1located .-substantially midway between the ends of the shoe which is the point of maximumfwear of the lining; The' lining is tapered. with a maximum. thickness at this center portion of: the shoe which isthe point of maximum pressure sothat greatest utilization is obtained of the lining," The location of the adjuster relatively to the levenhasfthe same advantage'cited for the connected with linkage 100 isthe trailing end or'an;

chored end ofsthe shoe, the anchoring-force of 16a being transmitted:throughdinkage 1G0 as applyingietfort on shoe 18a whichianchorsjon its-lever'36d connected-with pneumatic actuator 98. I In reverse, as W1 asiir-forv ward, both. shoes are applied with.substantiallyfequ al applying fforce; bothshoes are; self energizingand dqfa..."

, substantially equal; amount of the briaking work. The anchoringsurfaces on the leversfiajare disposed so that V a the center? of engagement pressure fof lthelshoes 16d 18a -with drum'fj surface 14a; is approximately;midway between the eridsi of, the shoes and the lining giiients are taperedso' that this is the location' of e the {maximum actu t n he l kst previous; embodiments, namely, fgoperation of the adjuster does not affect'the-pedal: stroke requirement for Each b ke shoe i -means of' springsjj tbstretched betweenopenings inthe I shoe-web and the aneho'rpins 38b so 'thatthe shoes rare urged 'retractivelylandlevers 36B are rotated on their 'pivotepin's untilbr ought intof engagemen t abutment .laterallyjppsitiouediby' mean of 1 projections and; 202 of the torque platefwhich are ."bent- 'nf oppq' ttejdirections to contact arespective one of th transverse strengthening Webs inord'erfto locate the" 46b which is formed from part of the torque plate, as previously described. Each pneumatic actuator 981) comprises a cylinder 2'94 defining an air chamber 206 and having a piston 208 slidably received therein. A link 210 with a wedge 212 at the end thereof is displaced by the piston 208 against the resistance of return spring 214 to rock the cams 216 and force them apart in the direction of shoe applying movement. A thrust member 218 is disposed between each cam follower 216 and lever 36b. Each thrust member has a conical section 220 received within a socket 222 of the lever 36b and at eachlateral side of the thrust member is an integral triangular lug 230, each of which contacts a rocker arm 232 which is seated against a fixed backing plate 234 secured to the torque plate 3%. Between each of the laterally spaced lugs 230 is a rounded end 250 which fits within a notched portion 252 of the cam follower 216.

The housing or cylinder 204 is mounted on the torque plate 3% by means of bolts 260 received through flange 262 and secured by nuts (FIGURE 8) 263 to the torque plate 305. When air pressure is communicated to the two actuators 9851 the pistons 298 are moved against the resistance of spring 214 to displace the link 210, causing the wedge 212 to force the cam followers 216 apart, the lateral component of the wedge action being resisted by rocker arms 232. The spreading force is communicated through the cam followers 216 to the thrust members 218 which cause the levers 36b to pivot on their pivot pins 38b so that, assuming counterclockwise rotation of the drum, corresponding to forward vehicle movement, the shoe 16b will anchor at its left end (FIG. 8) and the right end will be the leading end of the shoe; the shoe 18b will have its leading end at the left hand side of the shoe and the trailing or anchored end at the right side of the shoe. The anchoring force is taken through the levers 36b which distribute the anchoring force between abutments 46b and anchor pins 38b and the anchoring surfaces of the levers determine the location of the maximum pressure of engagement between the lining 22b and the drum which is located approximately midway between the ends of the shoes to obtain maximum-utilization of the lining.

In braking with opposite direction of vehicle movement the leading and trailing ends of the respective shoes reverse but the braking action is substantially the same as in forward vehicle movement so that the brake as a whole has approximately the same braking action in both forward and reverse vehicle movement. The levers 3612, while offering mechanical advantage multiplying the applying effort, do not require additional movement to fol low up for lining wear beyond that required for each increment of wear between adjustments. For example, should the lining 22b be substantially completely worn, the adjusters 56b can move the shoe outwardly to reestablish the original running clearance while the levers are maintained in their original position. Thus, the same stroke of piston will affect the same braking action. Since the levers are constrained to fixed path of pivotal movement, it is a relatively easy matter to translate this pivota1 movement to the axial and tangential movement required of the wedge 212. This is a marked advantage over pneumatic operation in which the cam followers are directly fastened to the brake shoes, since the pneumatic actuator must then follow the various motions required of the brake shoe during braking operation.

, Referring next to the embodiment shown in FIGURE 12, the inherent advantage of the invention enabling reduction of brake size will be set forth in a non-servo brake configuration which is suitable for small size trucks or even passenger cars.

In order to standardize the brake as far as possible, the user may, in the lighter duty trucks, remove one of the wheel cylinder actuators shown in FIGURE 1 and employ the brake as a leading shoe-trailing shoe combination sometimes referred to as a non-servo brake. The

It) brake structure shown in FIGURE 12 is substantially identical with that shown in FIGURE 1 except that one of the actuators (the one at the right hand side of the brake in FIGURE 1) is removed. As a result, the brake may be provided at even less cost and is still an acceptable solution where braking requirements are not as high.

In operation, assuming forward rotation of the vehicle corresponding to counterclockwise drum rotation, the shoe will be a leading shoe and provides self energizing braking action and the shoe provides trailing shoe or non-self-energizing braking action. In this case, the two shoes do not do an equal amount of the braking work and the brake is not as effective as the brake shown in FIGURE 1 where both shoes perform the same order of braking action as shoe 180. The brake is, however, substantially equally effective in forward and reverse vehicle movement. For example, when the vehicle is braked in reverse, this producing clockwise rotation of the drum, then the shoe 166 is an energizing or leading shoe brake and the brake shoe is a de-energizing or trailing shoe brake. Although the brake is not as effective as the one shown in FIGURE 1, various advantages of the brake configuration are nonetheless retained. For example, the anchoring load is distributed more efliciently just as in the embodiment of FIGURE 1 and therefore the brake components may be reduced in size and weight. The center of pressure between the shoe lining and opposing drum surface is approximately midway between thetwo shoe ends and therefore maximum utilization is obtained of the lining. The shoes are free floating, that is to say, both are pivotal and slidable at each of their opposite ends; and, both anchoring and applying forces are transmitted through a leverage system having an adjusting means which establishes the proper running clearance between the lining and opposing drum surface so that substantially the same piston stroke requirement exists throughout the life of the brakes. Since the piston of the fluid motor actuator does not follow out the shoe while it is being adjusted, the piston stroke is independent of the lining segment thickness and this lining segment thickness can be appreciable in heavy duty braking. As a result, the length of the wheel cylinder actuator need not be large even though some of its stroke is lost by acting through the intermediary of a lever.

In contrast with the embodiment shown in FIGURE 12 which represents the least eifective brake configuration, the brake embodiment shown in FIGURE 13 is an embodiment of the invention which is the most elfective brake configuration wherein the full anchoring force of one of the shoesis transmitted as applying effort on the other braking shoe. Thus, in place of one of the hydraulic actuators shown in FIGURE 1, there is substituted 2. strut 250 which is connected between the two levers 36d. The strut passes through aligned openings 252 of a fixed bracket 254 which is fastened to the torque plate 30d. 'Ihvo washers 256 are retained by rings 257 snapped within grooves 258 of the strut 250 so that movement of the strut in either direction through the opening will compress the spring 259 and tend to return the levers 360! to their original positions. Other than these modifications the structure is identical with that shown in FIG- URE 1.

In operation, assuming forward vehicle movement producing counterclockwise rotation of the drum 10d, the brake shoe 18d functions as the primary shoe and its anchoring force is transmitted through lever 36d and strut 254 to effect turning of lever 36d at the leading end of shoe 16d, both shoes then anchoring at the trailing end of shoe 16:! on its lever 36d. The anchoring force is distributed between the pivot bolt 38d and abutment 46d. In this embodiment, the brake configuration shown in FIGURE 13 is essentially different from FIGURE 1 in that servo action is introduced. The principal benefits of the invention are retained in that the anchoring surfaces provided by the levers can be so inclined and Q I ing to forward and reverse vehicle movement.

' position,

disposedto locate the point of maximum engagement 7 pressure at a point substantially midway between the'ends of the shoes. Thus the lining is tapered with a maximum thickness at this midway point and maximum utilization of lining is thereby obtained; The brake components are effectively and efliciently arranged by virtue of the fact that the applyingfferces and anchoring forces are passed through levers which are supportedat their opposite ends'to provide maximum strength and distribution of forces-within the brake. By thus avoiding concentration of braking and applying forces at-any one point overstressing can be efiectively prevented and the brake may be constructed of smaller and lighter weight componentsrfor a substantial; cost saving.

hydraulic actuator need not follow up lining wear and hence the actuator canbe made of shorter stroke length. While the two shoes 18d and 16d do not perform an equal amount of work in a given direction of braking, the brake is nonetheless equally eifective in over-all performance for each direction of drum rotation. Thus, iniforward vehicle movement the brake shoelfid does approxi 'r'nately one-thirdtheam ountof braking work as shoe 16d; 1

but, in reverse vehicle movement when theshoe 16d becomes the primary shoe and shoe 18d becemes the secondary shoe, the relative proportion of braking work distribution is now reversed with shoe 16d performing approximately one-third the amount of braking work of 18d. 1h rover-all operation, however, the braking per 'formance is substantially the; same both for counter- Although onlycertain selected embodiments of the in vention have been chosen for purposes 'of illustration, it

will be understood that these are in no way restrictive 'of' the invention. It is'reasonably to be'expected that those skilled in the. art can make variations and revisions' of the invention as will incorporate theherein disclosed prinbrake actuation and each'of said other ends of said'le'vers will engage said anchormeans in retracted position.

, shoes slidably arranged in end-t'o-end relationship on said I v .15 The adjusters 56d are located between the levers and the one end'of each shoe so that'pedal stroke of the 15; A brake comprising: a rotatable drum having a'cylindric'al braking surface; a stationary support member; brake stationary support; actuating means located between each pair of saidadjacent 'sh'oe'ends; abutment meanson each or saidadjacent shoe ends; four actuating levers each pivotally connected at one end to said support member and so arranged that'at least a portion of each is located between andengages a respective one of said abutment means and. said actuatingrneans; and anchor means operatively connected to said support member and so located thereon that the other end of two of said levers will engage said janchor meansto anchor thereon during brake actuation in one direction of drum rotation and the other end i of the other levers will engage said anchor means to anchor clockwise and clockwise rotation of the drum'correspond 7 ciples, and it is intended tliat such revisions and variations as incorporate the herein disclosed principles will beincluded within the scope'of'the following claims as equivalentsof theinvention, I

:What is claimed is? 1. In a brakez'a rotatable "drurnjhaving a cylindrical thereon during brake actuation when said drum is rotating in the opposite-direction, and each of saidother ends of said levers will engage said anchor means in retracted position. I a

' 6. The structure as recited in claim 5 wherein adjusting meansis provided at least one end of each shoe and includes said abutment means for varying the distance between each of said shoes'and said drum.

The structure asrecited in claim Swherein said actuating means comprises a fluidimotor having a pair of oppositely acting pistons and having thrust members operatively associated with a respective one of said levers for moving thesame and said shoes.

8. The structure as'recited in claim 5 wherein each shoe has both pivotal and sliding engagement at its opposite ends with said-levers to provide free, floating shoe movement. v I

9 .-In ja brakez a" rotatable drum having a'cylindrical bra-king surface a stationary support member, brake shoes .slidably arranged in eind-to-eLnd relationship on said stationary support, a'ctuati'ngmeans located between "a pair of said ladjacent shoe ends, an actuatinglever ivotally connected at oneend to said support member and so arbraking surface, a stationary support member, brake shoes slidably arranged in end-to-end relationship 'on said stationary support, actuating means located'b'etween a pair of said adjacent shoe ends, abutmentrneans on at least one of said adjacent shoe-,ends of one of said shoes, an

actuating lever pivotally connected 'at one .end to said a support member and so ararnged that at least a portion thereof is located between' and engages said abutment meansIand said actuating means, and anchor means separate from said actuating means and operatively connected to said support member and 50 located thereon thatthe other end of said lev'er will engage's'aid anchor means to anchor'the'reon duringbrake actuation in at least one.

direction and will engage said anchor means in retracted :2. 'I'he structure asrecited in' claim 1 whereinfadjustmeans including said abutment means is provided for. varying the distance-between said one shoe and said drurm 3. Thestructure as recitedin i'claim lwherein said actuating means'e'orriprises a fluid motor having athrust mem- 7 her operatively' associated with said lever for moving the 7 same and shoe;

. ranged that atleast a portiori thereof is locatedvbetween and engages abutment means at one. of said pair of ,ad-

' jaceiit, ends done of said brake shoes and said actuating means, said abutment means comprising a member carried by and extending from said 'one' shoe end, means for varying the distance saidlast named member extends from said one shoe end, and anchor means operatively, connected to said support member'for. receiving anchoring load frorn'the other end of said lever during-brake actuation inat least onedirectionof drurnrotation, and for 1 definingthe retracted positionfof said one shoe and, said leverp 10. The structure as recited in claim"9 wherein said actuating means comprises 'a' fluid motor h-avin'g a thrust member operatively associated withsaid lever for moving Y 411 a brake: a rotatabledrurn having a cylindrical:

' brakiiig'surfacaa stationary support member, brake shoes .slidably 'arr-anged i'n ehd-to-end relationship onsaid station- 1 ary support, aetu ating means locatedbetween a pair of said adjacentshoe ends, abutment means on each of'said pair of adjacent'shoe ends, a pair ofjactua'ting'levers each) pivotally cen nectedatone end to said support member;

' the sameandsaid shoe."

' 11. In at-brake: a rotatabledrum having a cylindrical braking'surface; astationary support member; brake shoes arrangediniend-to-end relationship on said stationary sup port; actuating means locatedbetweena pair of; said adjacent shoe ,endsyabutnient means on each of saidadjacent "shoe ends'ta pair. of a'ctuati-nglever each pivotally connected at one end to said supportmemberiand so'arranged that at. least ajportion 'of e'ach islocated between and engages a respectiveione ofsaid abutment means'and said actuating means; at least one'of said abutment'means comprisinga member carried by 'andextending from its respective shoe end, m'eans for varying thejdistancejsaid last named member extends from its respectiveshoe end; and

anchor means operatively connected to said support memher for receiving anchoring load from the opposite end of one of said levers during brake actuation in one direction of drum rotation and for receiving anchoring load from the opposite end of the other of said levers during brake actuation when said drum is rotating in the opposite direction, and for defining the retracted position of said shoes and said levers.

12. The structure as recited in claim 11 wherein said actuating means comprises a fluid motor having a pair of oppositely acting pistons and having thrust members operatively associated with a respective one of said levers for moving the same and said shoes.

13. The structure as recited in claim 11 wherein each shoe has both pivotal and sliding engagement at its opposite ends with said levers to provide free floating shoe movement.

14. A brake comprising: a rotatable drum having a cylindrical braking surface; a stationary support member; brake shoes slidably arranged in end-to-end relationship on said stationary support; actuating means located between one pair of said adjacent shoe ends; abutment means on each of said adjacent shoe ends; four actuating levers each pivotally connected at one end to said support member with one pair of said levers being so arranged that at least a portion of each is located between and engages a respective abutment means of said one pair of said adjacent ends and said actuating means; the other pair of levers being so located that the abutment means of the other pair of adjacent shoes ends will engage at least a portion of a respective one of said other pair of levers; and anchor means operatively connected to said support member and so located thereon that the other end of one of said one pair of levers will engage said anchor means to anchor thereon during brake actuation in one direction of drum rotation and the other end of the other lever of said one pair of levers will engage said anchor means to anchor thereon during brake actuation when said drum is rotating in the opposite direction, and each of said other ends of one pair of said levers will engage said anchor means during retracted position; and means interconnecting said other pair of levers for communicating thrust therebetween as applying effort, and means for retracting said shoes.

' 15. A brake comprising: a rotatable drum having a cylindrical braking surface, a stationary upport member, brake shoes slidably arranged in end-to-end relationship on said stationary support, actuating means located between one pair of said adjacent shoe ends, four actuating levers each pivotally connected at one end to said support member with two of said levers being so arranged that at least a portion of each is located between and engages abutment means at a respective one of said adjacent ends of said brake shoes and said actuating means, and anchor means operatively connected to said support member and so located thereon that the other end of the other two of said levers will engage said anchor means to anchor thereon during brake actuation in each direction of drum rotation and each of said other ends of all said levers will engage said anchor means during retracted position.

16. The structure as recited in claim 5 wherein said actuating means is mechanical.

17. In a brake: a rotatable brake drum, a stationary support, a pair of brake shoes slidably arranged in endto-end relationship on said support, at least one of said shoes comprising a rim with a pair of axially spaced transverse webs, actuating means located between a pair of adjacent ends of said shoes, at least one actuating lever pivotally mounted at one end on said support, abutment means on at least one endof said one brake shoe, said lever having at least a portion thereof located between and engaging said actuating means and said abutting means, anchoring means for taking anchoring torque I from said lever, said lever further having a portion thereof disposed between the ends of said axially spaced webs whereby said one shoe is axially guided by said lever. 18. The structure as recited in claim 4 wherein said anchor means is separate from said actuating means.

19. The structure as recited in claim 9 wherein said anchor means is separate from said actuating means.

20. In a brake: a rotatable drum having a cylindrical braking surface, a stationary support member, brake shoes slidably arranged in end-to-end relationship on said stationary support, actuating means located between a pair of said adjacent shoe ends, an actuating lever pivotally connected at one end to said support member and so arranged that at least a portion thereof is located between and engages abutment means at one of said pair of adjacent ends of one of said brake shoes and said actuating means, said abutment means comprising a member carried by and extending from said one shoe end, means for varying the distance said last named member extends from said one shoe end, and anchor means operatively connected to said support member for defining the retracted position of said one shoe and said lever, said anchor means being arranged to be engaged by the other end of said lever.

21. The structure as recited in claim 20 wherein said anchor means is separate from said actuating means.

References Cited in the file of this patent UNITED STATES PATENTS 2,372,415 Eksergian Mar. 27, 1945 2,385,168 Stelzer Sept. 18, 1945 2,487,756 House Nov. 8, 1949 2,777,542 Russell Jan. 15, 1957 2,818,140 Roller Dec. 31, 1957 2,822,065 Goepfrich et a1 Feb. 4, 1958 2,867,297 White Jan. 6, 1959 2,906,517 Goepfrich Sept. 29, 1959 3,023,852 Powlas Mar. 6, 1962 FOREIGN PATENTS 785,864 Great Britain Nov. 6, 1957 

1. IN A BRAKE: A ROTATABLE DRUM HAVING A CYLINDRICAL BRAKING SURFACE, A STATIONARY SUPPORT MEMBER, BRAKE SHOES SLIDABLY ARRANGED IN END-TO-END RELATIONSHIP ON SAID STATIONARY SUPPORT, ACTUATING MEANS LOCATED BETWEEN A PAIR OF SAID ADJACENT SHOE ENDS, ABUTMENT MEANS ON AT LEAST ONE OF SAID ADJACENT SHOE ENDS OF ONE OF SAID SHOES, AN ACTUATING LEVER PIVOTALLY CONNECTED AT ONE END TO SAID SUPPORT MEMBER AND SO ARARNGED THAT AT LEAST A PORTION THEREOF IS LOCATED BETWEEN AND ENGAGES SAID ABUTMENT MEANS AND SAID ACTUATING MEANS, AND ANCHOR MEANS SEPARATE FROM SAID ACTUATING MEANS AND OPERATIVELY CONNECTED TO SAID SUPPORT MEMBER AND SO LOCATED THEREON THAT THE OTHER END OF SAID LEVER WILL ENGAGE SAID ANCHOR MEANS TO ANCHOR THEREON DURING BRAKE ACTUATION IN AT LEAST ONE DIRECTION AND WILL ENGAGE SAID ANCHOR MEANS IN RETRACTED POSITION. 